Electrical testing



June 13,1944. G. MAKUH y 2,351,441

ELECTRICAL TESTING 'I Filed Jan. 27, 1940 POLARITY SVV.

CAM LODE CAM DWLLL ADQ. *ze TEST y uw vGeorge Mokuh, INVENTQR BYZM, Mfw/f ATToRN Lw Patented June 13, 1944 UNITED STATES PATENT OFFICE ELECTRICAL TESTING George Makuh, Cleveland, Ohio, assignor to Electric Heat Control Company, Cleveland, hio,' a corporation of Ohio Application January 27, 1940, Serial No. 315,873 f 9 claims.. (cl. 177-311) The invention relates to electrical testing and particularly to a method and-means "for testing the breaker means of an ignition system'oian internal combustion engine, and, more' particularly, it relates to a method 'and means whereby cam dwell may bel determined, that is, during i what part of the rotation of the cam of the breaker means the contacts of the breaker means are permitted to be in'engagement. The principal object of the invention is the improvement of methods and means of these types.

In the drawing accompanying this *specifica-A- tion, and forming a part of this application, there is shown, for purposes of illustration, one embodiment of the invention. In the drawing:

Figure 1 is a plan view of apparatus embodying the invention, Figure 2 is an electrical circuit diagram of apparatus embodying'the invention, which shows also a portion of an ignition system and how the apparatus may be connected to the tem to test the latter, and

Figures 3, 4, and 5l are enlarged plan views showing the scale of an instrument forming part of the embodiment shown in Figure 1, and showignition sy'sing also the pointer of the instrument in diierent positions with respect to the scalein the respective views.

The embodiment of the testing apparatus illus- -trated in the drawing comprises a portable casing I0 which may be provided with a bail I I whereby the casing can be conveniently hung from a portion of the automotive vehicle the ignition syste of which is to be tested.

`Carried by the casing I0 is an electroresponsive indicating means or meter I2,y the actuating t.

a movable contact I5 (Figure 2), operable from the exterior of the casing l0 by means of a rotatable knob I6. Near the knob I6 the casing conveniently bears the legend Cam lobel adj. Within the casing I3 is also suitably mounted a switch II (Figure 2) 'for changing the connec- I tions of parts of the electrical system to different test positions, in one of which positions the amount of cam dwell may be read in degrees on the scale I3. The cam dwell test switch I'I is of the push button type provided with a push button I3 which is normally biased upwardly (that is, toward the observer of the plan viewof Figure 1) by a spring I9. Near the pushbutton I8 the casing I0 conveniently bearsthe legend Cam dwell test. Within the casing is also suitably mounted a reversing or polarity switch l20 (Figure v 2) having an' operating .lever Ior knobf 2I (Figure 1) disposed at the outside ofV the casing I 0. The lever 2| lis connected-to a shaft 22 extending through the casing I0 vtothe reversing switch, the shaft-22 beingvrotatable'totwo 'different positions, one'clockwise and one counterclockwise, from the oil position shown in Figure l. The casing I0 is also provided with a lens 23, behind which, within the casing is suitably mounted an indicating lamp 24 (Figure 2).- For convenient connection .of the testing'apparatus to an ignition system to be tested, three exible conductors 25,'26, 2'I are connected-respectively to attaching 'clamps or 'connectors 28, 29, :3,0 adapted for quick connection and disconnection, or ofyany other's'uitable'iorm; The clamps28,

29, 3S are respectively'intended for connection to ground batteryf and distributor of the ignition'system and hence respectively bear'the legends Grdj Battj and Dist.- The conductors 25, 26, 21 maybe constructed and'arranged as a single flexible cable 3| where they emerge from the'casing I0, andior .the desired remainder of their length'they are separate. Referring now to Figure 2, the cam dwell test switch II is here shown as comprising amovable contact 32 biased by thespring I9 into engagement with a pair of contacts 33, 34. When `the push button 'I3 is depressed the movable contact 32 is adapted to engage a pair of contacts 35, 36. The contacts 33, 35 are connected by means of a jumper 3'l,so that in either position of the movable Contact 32, one end of the movable contact is electrically connected to the jumper, whereas the other end of the movable contact is connected either to the contact 34 or the contact 3S; and it is accordingly apparent that other forms of switches performing the same function may be utilized. The reversing or polarity switch 2B is here shown as comprising an arcuate insulating member 38 mounted'V to be' rotatable by the rotatable shaft '22. On the insulating member y38k are mounted two arcuate conducting members 39, 40 each of which comprises a respective integral projection 4 I, 42; The construction and arrangement is such that when the shaft 22 is rotated clockwise to rotate the member 38 to a limiting position, the projection 4| engages a relatively stationary contact 43 and the projection 42 engages a relatively stationary contact 44. On the other hand, if the member 38 is rotated by the shaft 22 in a counterclockwise direction from the position shown in Figure 2, the projection 4| engages a relatively stationary contact 45 and the projection 42 engages a relatively stationaryV contact 46. The reversing switch 20 is also provided with contacts or brushes 41, 48 with which the arcuate conducting 39, 4I) are respectively in sliding engagement, so that in any position of the reversing switch the brushes 41, 48 are in contact with the arcuate conducting members 39, 49 respectively.

A resistor 49 has its terminals connected respectively to the brush contacts 41, 48 of the reversing switch. The contact 41 of the reversing switch is connected by a conductor 50 to the jumper 31. The contact 4B of the reversing switch is connected to the conductor 26 and hence to the clamp 29, this clamp being diagrammatically indicated in Figure 2 by an arrow, the clamps 2B, 30 being likewise so indicated.

The meter I2 has one terminal connected, by a conductor 5| and a jumper 52, to the relatively stationary contacts 44, 45 of the reversing switch, and has its other terminal connected by a con.- ductor 53 to the adjustable contact I5 the latter `cooperating with a resistor 54. The adjustable contact I5 is movable along the resistor 54 when the knob I6 isv rotated. A relatively high resistance 55 may be interposed in the conductor 53. One terminal of the resistor 54 is connected through a resistor 56 to the jumper 52, and hence the meter I2 is adjustably connected in shunt with the resistors 54, 56. The other terminal of the resistor 54 is connected through a conductor 51 to cathodes 58 of a rectier 59 of the thermionic type, anodes 60 of the rectifier 59 being connected by a conductor 6I to a jumper 62' which connects the relatively stationary contacts 43, 46 of the reversing switch. A rectifier of the thermionic type is preferred because within desired limits the current therethrough will be proportional to the impressed electromotive force. I! desired the resistor 54 may have connected in shunt therewith a resistor 63 of suitable resistance to desirably control the fallv of potential in the resistor 54. The rectifier 59 is provided with a filament 64 for heating the cathodes 58, one terminal of the filament being connected by a conductor 65 to the contact 34 of the cam dwell test switch I1 and the other terminal being conf portion of the rotation of a cam 10 (driven by f the engine, not shown) When the breaker arm is permitted by the cam to dwell in the position in which the contacts 68, 69 are in engagement. For purposes of illustration merely, the cam 10 is here shown `as having six lobes. tively stationary contact 69 is connected by a conductor 1| to one terminal of a primary 12 of a spark coil, the other terminal of the primary vbeing connected by a conductor 13 to one of the The other terminal r terminals of a battery 14. of the battery 14 may be grounded to the frame 'Ihe relai of the vehicle, as indicated at 16, and conductively connected by the frame, or a conductor 15, to the breaker arm 61. The spark coil is here shown as provided with a secondary 11, one terminal of which is connected to the conductor 13 and the other terminal of which leads to a distributing contact arm (not shown) as is well known in the art. 'Ihe contacts 68, 69 of the breaker mechanism are shunted by a condenser 18.

When it is desired to test an ignition system of an engine, the system is left intact on the vehicle in completely operative condition, and, with reference to Figure 2, the clamp 28, marked Grd is connected to the ground of the ignition system, for example to the grounded terminal of the battery 14; the clamp 29, marked Batt, is connected to the other terminal of the battery 14; and the clamp 30, marked Dist is connected to the conductor 1I, the latter connection being conveniently made by connecting the clamp 30 to that conducting terminal of thev distributor which is connected to the relatively stationary contact 69.

When the foregoing connections have been made, and with the parts as shown in Figures 1 and 2, the pilot lamp 24 will be illuminated, indicating that the filament 64 is receiving energy from the battery 14 and that. the resistor 49 is connected in shunt with the battery. The shunt circuit in which the resistor 49 is included is from the terminal of the battery to which the clamp 29 is connected, through the conductor 26, through the resistor 49, through the conductor 50, the jumper 31, the relatively stationary contact 33, the'movable contact 32, the relatively stationary contact 34, the conductor 25, to the clamp 28 to the other terminal of the battery. The meter I2 however receives no energy at this time, assuming that the polarity switch is in the position shown in Figures 1 and 2, and consequently the needle I4 of the meter reads 0, as indicated in Figure 3. The opera-tor may now turn the polarity switch lever 2| clockwise,for example. This causes the projections 4I and 42 to engage the contacts 43, 44 respectively. This connects the left hand terminal of the resistor 49 to the anodes 60 by way of the brush contact 41, the conducting member 39, the projection 4I, the contact 43 and the conductor 6I, and connects the right handv terminal of the resistor 49 to the cathodes 58 by way of the brush contact 48, the conducting member 40, the projection 42, the contact 44, the jumper 52, vresistors 56, 54,l 63, and conductor 51. However, if the fall of potential in the resistor 49 is not in the correct direction the rectifier 59 will not permit current now through resistors 54, 56, 63 and hence the needle I4 of the meter I2 Will show no deflection. The direction of fall of potential in resistor 49 will of course depend upon which pole of the battery 14 is grounded. If the needle I4 shows no deflection the operator then turns the lever 2| of the polarity switch counterclockwise so that it occupies its other operative position, whereupon the needle I4 of the meter will be deflected, in a clockwise direction as viewed in lthe drawing, an amount dependent on the voltage of the battery 14 and the resultant current in the circuit of the electroresponsive operating means of the meter I2. When the lever 2| of the polarity switch is turned counterclockwise, as hereinbefore assumed, the projection 4I will then be in engagement with the contact 45, and the projection 42 will be in engagement with the contact 46. Thisr establishes a circuit in shunt with the resistor 49, from the left hand terminal of theresistor 49, through the brush contact 41, the arcuate conducting member 39, the projection 4I, the relatively stationary contact 45, the jumper 52, the resistor 5B, the resistors 54, 63 in' parallel, the conductor 51, the cathodes 58, the anodes 60, the conductor 6|, the jumper 62, the relatively stationary contact 4B, the projection 42, the arcuate member 40, the brush contact 48, to the right hand terminal of the resistor 49. I It will vbe evident that since the meter II2 is connected in shunt with the resistors 54, 56 that the amount of current owing in the meter circuit will be proportional to the fall of potential in the resistors 54, 56 and this fall of potential iis in turn dependent upon the fall of potential in the resistor 49. After the operator has manipulated the polarity switch lever 2l to the proper position to "cause a deflectionoi the needle I4 of the meter I2, he turns the knob I6 for cam lobe adjust- 'rnentpthereby movingf the contact I5 along the resistor V54, in such a direction that, and until, the needle I4 indicates 60, as shown in Figure 4. The reading of the needle lil is so adjusted by lthe cam lobe adjustment knob I, because, in the instance under consideration, the cam lll is la six lobe cam and each lobe occupies one-sixth fof the entire circumference.

It will be understood that the engine is in operation, and when the foregoing adjustments have been made, the operator depresses the button I8 of the cam dwell test switch, thereby icausing the movable contact 32 to engage the contacts 35. Thelamp 24 and dla-ment 64 continue to be supplied with current as before, but the aforesaid movement of contact 32 interrupts the connection between the left hand terminal of the resistor 4Q to the conductor 25, and, instead, completes a connection from the left hand terminal of the resistor 49 to the conductor 2.' and clamp 39. The right hand terminal of the resistor 49 remains connected, through the clamp. 29, to one terminal of the primary 1.2, and since the clamp is connected to the other terminal of the primary 12', operation of -the cam dwell test switch Il connects the resistor 49 .in shunt with the primary "IZ of the spark coil. Consequently, inasmuch as the engine is operating, current will ow through the .primary '12, and through the resistor 49, only when the contacts 68, B9 are permitted to remain in engagement by the cam lll. In view of the previous adjustment of the needle I4 to a deection of 60 at a time when the resistor 49 .is continuously receiving current by reason of beingy shunted across the battery 14, the needle i4 will now indicate some lesser number of degrees, as shown for example in Figure 5, this number of degrees indicating the lnumber of degrecs of rotation of the cam 'lll during which it permits the contacts G8, 69 to remain closed VVper lobe ofthe cam. Ii the number of degrees indicated by the needle I4, as in Figure 5, is an Iunsatisfactory amount, the operator may adjust `the breaker mechanism, as, for example, by ad.- v,iustingltlie rela-tively stationary contact 59, again read the meter I2 when the button I8 is depressed, and so on, until the number of degrees cam dwell is satisfactory.

It will be no-ted that whenever the cam dwell test button I8 is released the resistor 49 is connected in shunt with the battery 14, thereby enabling a quick check on the cam lobe adjustment throughout the testing operations. If at any time during the testing operations it is noted that the needle I4 does not read 60 when the button I8 is released, the cam lobe adjustment knob l5 is manipulated to make it so read. Connection of the resistor 49 in shunt with the primary 'l2 will not affect proper operation of the ignition system to maintain the engine running if the resistance of the resistor 49 is suitably chosen. A resistance of 125 ohms has been found satisfactory, but it is not to be understood that the invention is limited to use of that particular value, since any suitable value may be used which will not cause too much current to be shunted away from the primary 12.

It will be evident that but a single scale I3 is necessary to test ignition systems having cam lobes of any usual number. The cam dwell in degrees is readable on this single scale no matter how many lobes the cam may have which is being tested. The scale is desirably so chosen that from 0 to full scale the number of degrees on the scale is equal to 350 divided by the number oi lobes on a cam having the lowest number of lobes desired to be tested. In the instance illustra-ted full scale is and this range is suitable for all practical purposes. As a matter of convenience for operators the scale is provided with numbers 4, 6, 8, and 12, corresponding to the usual numbers of cam lobes, at the number of degrees on the scale I3 respectively equal to 360 divided by 4, 6. 8, and 12. The scale I3 'may bear, desirably on the arc in which the numbers 4. 6, and 12 are located, the legend Set cam lobe adjust, and all that the operator need remember is to set the cam lobe adiustment knob I3 so that the needle I4 will read 4r, 6, 8,

vor l2, depending upon the number of lobes of the cern of the breaker mechanism being tested. It is of course apparent that these cam lobe numbers on the scale I3 are not essential.

From the foregoing it will be apparent to those skilled in the art that the illustrated embodiment of the invention provides a new and improved method of. and a new and improved means for, electrical testing. and accordingly, accomplishes the principal object of the invention. On the other hand. it also will be obvious to those skilled in the art that the illustrated embodiment of the invention may be variously changed and modined, or features thereof, singly or collectively, embodied in other combinations than those illustrated, without departing from the spirit of the invention, or sacrificing all of the advantages thereof. and that accordingly, ythe disclosure herein is illustrative only, and the invention is not limited thereto.

I claim:

1. Means for measuring the dwell of the breaker means of an ignition system for an internal combustion engine, system having a primary circuit connected to a source of current, the parts of said circuit including said,I breaker means and induction coil primary. inseries, comprising:

' resistor means eiering substantially the same resistance to current ow for either direction of current flow therethrough; means for connecting .said resistor rnc-ans directly across one of said parts of said nriinary circuit: a circuit connected across said resistor means. said measuring circuit comprising electroresponsive indicating means in series with a rectifier permitting substantial current flow through. said electroresponsive indicating means in one direction only..

2. Means for measuring the dwell of the breaker means of an ignition system for an internal combustion engine, said system having a primary circuit connected to a source of current, the parts of said circuit including said breaker means and an induction coil primary in series, comprising: resistor means ciiering substantially the` same resistance to current iiow for either direction of current flow therethrough; means for connecting said resistor means directly across said primary coil; and a measuring circuit connected across said resistor means, said measuring circuit comprising electroresponsive indicating means in series with a rectifier permitting substantial current iiow through said electroresponsive indicating means in one direction only.

3. Means for measuring the dwell of the breaker means of an ignition system for an internal combustion engine, said system having a primary circuit connected to a source of current, the parts of said circuit including said breaker means and an induction coil primary in series, comprising: resistor means oiiering substantially the same resistance to current flow for either direction of current flow therethrough; means for connecting said resistor means directly across one of said parts of said primary circuit; and a measuring circuit connected across said resistor means, said measuring circuit comprising electroresponsive indicating means in series with a thermionic rectifier permitting substantial current iiow through said electroresponsive indicating means in one direction only.

4. Means for measuring the dwell of the breaker means of an ignition system for an internal combustion engine, said system having a primary circuit connected to a source of current, the parts of said circuit including said breaker means and an induction coil primary in series, comprising: first resistor means offering substantially the same resistance to current flow for either direction of current dow therethrough; means for connecting said first resistor means directly across one of said parts of said primary circuit; and a measuring circuit connected across said rst resistor means, said measuring circuit comprising second resistor means, offering substantially the same resistance to current flow for either direction of current flow therethrough, in series with a rectifier permitting substantial current flow through said second resistor means in one direction only, and further comprising electroresponsive indicating means connected across a selected portion of said second resistor means, and means for adjusting the selected amount of said second resistor means across which said electroresponsive indicating means is connected while leaving the resistance to current flow through said measuring circuit substantially unchanged.

5. Means for measuring the dwell of the breaker means of an ignition system for an internal combustion engine, said system having a primary circuit connected to a source of current, the parts of said circuit including said breaker means and an induction coil primary in series, comprising: first resistor means offering substantially the same resistance to current flow for either direction of current flow therethrough; means for connecting said first resistor means directly across said primary coil; and a measuring circuit connected across said first resistor means, said measuring circuit comprising second resistor means, offering substantially the same resistance to current flow for either direction of current iiow therethrough, in series with a rectifier permitting substantial vcurrent iiow through said second resistor means in one direction only, Aand further comprising electroresponsive indicating means connected across a selected portion of said second resistor means, andmeans for adjusting the selected amount of said second resistor means across which said electroresponsive indicating means is connected while leaving the resistance to current flow through said measuring circuit substantially unchanged.

6. Means for measuring the dwell of the breaker means of an ignition system for an internal combustion engine, said system having a primary circuit connected to a source of current, the parts of said circuit including said breaker means and an induction coil primary in series, comprising: first resistor means offering substantially the same resistance to current flow for either direction of current flow therethrough; means for connecting said first resistor means directly across one of said parts of said primary circuit; and a measuring circuit connected across said iirst resistor means, said measuring circuit comprising second resistor means, loiering substantially the same resistance to current flow for either direction of current flow therethrough, in series with a thermionic rectifier permitting substantial current flow through said second resistor means in one direction only, and further comprising electroresponsive indicating means connected across a selected portion of said second resistor means.

'7. Means for measuring the dwell of the breakerl means of an ignition system for an internal combustion engine, said system having a primary circuit connected to a source of current, the parts of said circuit including said breaker means and an induction coil primary in series, comprising: nrs-t resistor means offering substantially the same resistance to current iiow for either direction of current flow therethrough; means for connecting said first resistor means directly across one of said parts of said primary circuit; and a measuring circuit connected across said rst resistor means, said measuring circuit comprising second resistor means, ofering substantially the same resistance to current dow for either direction of current now therethrough, in series with a thermionic rectifier permitting substantial current flow through said second resistor means in one direction only, and further comprising electroresponsive indicating means connected across a selected portion of said second resistor means, and means for adjusting the selected amount of said second resistor means across which said electroresponsive indicating means is connected while leaving the resistance to current ow through said measuring circuit substantially unchanged.

8. Means for measuring the dwell of the breaker means of an ignition system for an internal combustion engine, said system having a primary circuit connected to a source of direct current, the parts of said circuit including said breaker means and an induction coil primary in series, comprising: an instrument having one scale only, said scale being graduated from zero to a number of degrees equal to 360 degrees divided by the number of lobes on a cam having the least number of lobes desired to be tested; said instrument comprising a pointer constructed and arranged to traverse said scale, and comprising electroresponsive means ior actuating said pointer; circuit means in which said electroresponsive means is included; connection means for connecting said circuit means across said source of current so as to feed said electroresponsive means with continuous electric current; said circuit means including means for adjusting the ow of said continuous current through said electroresponsive means to cause said pointer to indicate on said scale that number of degrees corresponding to 360 degrees divided by the number of lobes of the cam of the breaker means to be tested whether said cam of the breaker means to be tested has said least number of lobes or a greater number of lobes; and said circuit means including means so constructed and arranged that When said connection means is connected across one of said parts of said primary circuit after the aforesaid.y adjustment has been made said pointer indicates on said scale the number of degrees per lobe that said cam to be tested permits the contacts of the breaker means to remain in engagement while said breaker means is in operation.

9. Means for measuring the dwell of the breaker means of an ignition system for an internal combustion engine, said system having a primary circuit connected to a source of direct current, the parts of said circuit including said breaker means and an induction coil primary in series, comprising: an instrument having one scale only, said scale being graduated from zero to a highest number of degrees equal to 360 degrees divided by the number of lobes on a cam having the least number of lobes desired to be tested, the graduation mark for said highest number of degrees bearing the same numeral as said highest number and also the same numeral as said least number of lobes, and certain graduation marks of said scale intermediate zero and said highest number bearing numerals respectively the same as numbers of cam lobes greater than said least number of cam lobes said certain graduation marks being in each instance that number of degrees which corresponds to 360 degrees divided by the respective number of cam lobes; said instrument comprising a pointer constructed and arranged to traverse said scale, and comprising electroresponsive means for actuating said pointer; circuit means in which said electrorespcnsive means is included; connection means for connecting said circuit means across said source of current so as to feed said electroresponsive means with continuous electric current; said circuit means including means for adjusting the flow of said continuous current through said electroresponsive means to cause said pointer to indicate on said scale that graduation bearing the numeral the same as the number of lobes of the cam of the breaker means to be tested whether the cam of the breaker means to be tested has said least number of lobes or a greater number of lobes; and said circuit means including means so constructed and arranged that when said connection means is connected across one Iof said parts of said primary circuit after the aforesaid adjustment has been made said pointer indicates on said scale the number of degrees per lobe that said cam to be tested permits the contacts of the breaker means to remain in engagement while said breaker means is in operation.

GEORGE MAKUH. 

